Systems and methods for implementing and manufacturing reticles for use in photolithography tools

ABSTRACT

Methods, systems, and tool sets involving reticles and photolithography processing. Several embodiments include obtaining qualitative data from within the pattern area of a reticle indicative of the physical characteristics of the pattern area. Additional embodiments include obtaining qualitative data indicative of the physical characteristics of the reticle remotely from a photolithography tool. In further embodiments qualitative data is obtained from within the pattern area of a reticle in a tool that is located remotely from the photolithography tool. Several embodiments provide data taken from within the pattern area to more accurately reflect the contour of the pattern area of the reticle without using the photolithography tool to obtain such measurements. This is expected to provide accurate data for correcting the photolithography tool to compensate for variances in the pattern area, and to increase throughput because the photolithography tool is not used to measure the reticle.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. application Ser. No. 11/217,888filed Sep. 1, 2005, now U.S. Pat. No. 8,029,947, which is incorporatedherein by reference in its entirety.

TECHNICAL FIELD

The present invention is directed to methods and apparatus formanufacturing and implementing reticles for use with scanners, steppers,and other photolithography tools. Many embodiments of the invention aredirected to reticles used in the manufacturing of semiconductor devices,microlenses, micro-mechanical devices, micro-electronic devices, andother types of micro-feature devices.

BACKGROUND

Micro-feature devices have a large number of very small features thatare typically formed in and/or on wafers or other types of workpieces byselectively removing material from the wafer and/or depositing materialonto the wafer. For example, features are often formed by (a)constructing a pattern in a layer of resist to form a mask on the wafer,(b) etching holes and/or trenches in the wafer through openings in themask, and (c) filling the resulting features with dielectric,semiconductive, and/or conductive materials. Photolithographic processesare generally used to transfer the intricate patterns of the featuresonto discrete areas of the layer of resist.

A typical photolithographic process includes depositing a layer ofradiation-sensitive photoresist material on the wafer, positioning areticle having a mask pattern over a selected area of the photoresist,and then passing an imaging radiation through the reticle to expose thephotoresist in the configuration of the mask pattern. A developer, suchas an aqueous base or a solvent, is used to remove either the irradiatedareas or the masked areas of the photoresist. For example, when theradiation changes the photoresist from being generally soluble in thedeveloper to generally insoluble, then the developer removes the maskedportions of the resist layer. Alternatively, when the radiation changesa photoresist from being generally insoluble in the developer to begenerally soluble, then the developer removes the exposed portions ofthe photoresist.

Existing lithography processes are capable of creating very complexpatterns of extremely small features across the surface of a wafer toform the trenches, vias, holes, implant regions, conductive lines,gates, and other features on a wafer. In a typical application, alithographic tool transfers the pattern in the reticle to the workpieceby scanning or stepping the pattern across precise areas of theworkpiece. As microelectronic devices become more complex, there is adrive to continually decrease the size of the individual features andincrease the density of the features across the wafer. Thissignificantly increases the complexity of lithographic processingbecause it is increasingly difficult to accurately focus the patternonto the face of the wafer. In many applications, the depth of field forfocusing the pattern on the wafer is so small that slight variations inthe wafer surface and/or the reticle can adversely affect the quality ofthe pattern transferred to the wafer.

One conventional process to compensate for non-uniformities in reticlesis to measure the flatness of the reticles in the photolithography toolbefore processing the wafers. The topography of the reticles isconventionally measured by detecting light that passes through alignmentmarks in a perimeter region outside of the pattern area of the reticle.Based on the topographical data of the alignment marks in the perimeterregion around the pattern area of the reticle, the topography of thepattern area is estimated. Conventional lithographic tools are thenadjusted by tilting the wafer stage and/or adjusting the optics tocompensate for variances in the estimated pattern area of the reticle(e.g., the estimated curvature of the reticle).

One problem with such conventional processes is that the topography inthe pattern area of the reticle is estimated based on the alignmentmarks in the perimeter region of the reticle. As the feature sizesdecrease, this may not provide sufficiently accurate data to compensatefor non-uniformities in the pattern area. Moreover, lithographic toolsare extremely expensive and it is very costly to use lithographic toolsfor measuring the non-uniformities in the reticle. Such use oflithographic tools is expected to reduce the throughput of processingwafers because the time period for qualifying the reticles iseffectively downtime for processing wafers. Therefore, there exists aneed to improve conventional photolithographic processes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart of a method for manufacturing a reticle inaccordance with an embodiment of the invention.

FIG. 2A is a schematic view of a procedure for obtaining qualitativedata from within a pattern area of a reticle at a location remote from aphotolithography tool in accordance with an embodiment of the invention.

FIG. 2B is a schematic view of a reticle being processed in accordancewith several embodiments of the invention.

FIG. 3 is a flow chart of a method for implementing a reticle in aphotolithography tool in accordance with an embodiment of the invention.

FIG. 4 is a schematic illustration of a system for implementing areticle in a photolithography tool in accordance with severalembodiments of the invention.

FIG. 5 is a flow chart of a method for implementing a reticle in aphotolithography tool in accordance with another embodiment of theinvention.

FIG. 6 is a flow chart of a method for implementing a reticle in aphotolithography tool in accordance with still another embodiment of theinvention.

FIG. 7 is a flow chart of a method for processing a micro-device waferin accordance with an embodiment of the invention.

DETAILED DESCRIPTION A. Overview

The present invention is directed toward methods, systems and tool setsfor manufacturing and/or implementing reticles in photolithographyprocessing. Several embodiments of the invention are directed towardobtaining qualitative data indicative of the physical characteristics ofa reticle from within the pattern area and/or a perimeter region.Additional embodiments of the invention are directed toward obtainingqualitative data indicative of the physical characteristics of thereticle remotely from a photolithography tool. These two aspects of theinvention can be combined in further embodiments in which qualitativedata is obtained from within the pattern area of a reticle using ameasurement tool located remotely from the photolithography tool. As aresult, several embodiments of methods and systems in accordance withthe invention provide data taken from within the pattern area to moreaccurately reflect the features of the pattern area of the reticlewithout using a photolithography tool to obtain such measurements. Thisis expected to provide more accurate data for adjusting photolithographytools to compensate for variances in the pattern area, and it isexpected to enhance the productivity of such photolithography toolsbecause they can process production wafers instead of calibrating thereticle.

Several embodiments of the invention are directed toward methods formanufacturing a reticle for use in a photolithography tool. Oneparticular embodiment of such a method comprises providing a substratehaving a pattern area and a perimeter region outside of the patternarea. This method continues by obtaining qualitative data indicative ofphysical characteristics of the substrate from points or regions withinthe pattern area and/or the perimeter region. The qualitative data, forexample, can be a measurement of the contour or non-uniformities of thereticle from several points within the pattern area. The qualitativedata is preferably obtained remotely from the photolithography tooleither before or after forming a pattern in the pattern area of thereticle. After the qualitative data has been obtained, the methodcontinues by determining a correction model based at least in part onthe qualitative data to apply to the photolithography tool. Thecorrection model, for example, can be used to adjust the position of thewafer stage and/or adjust the optics of the photolithography tool tocompensate for the unique physical characteristics of the particularreticle.

Several other embodiments of the invention are directed towardimplementing a reticle in a photolithography tool. One particularembodiment of such a method includes obtaining topographical data fromwithin the pattern area of the reticle. The pattern area, for example,is the portion of the reticle through which an exposure radiation is tobe directed for transferring a pattern from the reticle to a wafer. Thetopographical data is preferably obtained remotely from thephotolithography tool either before or after forming a pattern in thepattern area of the reticle. This method continues by determining acorrection model and applying the correction model to thephotolithography tool to adjust for the topography or other uniquephysical characteristics in the pattern area of the reticle. Thecorrection model is determined at least in part from the topographicaldata obtained from within the pattern area.

Another embodiment of a method for implementing a reticle in aphotolithography tool comprises obtaining qualitative data from within apattern area of the reticle. This method continues by determining acorrection model to apply to the photolithography tool from thequalitative data, and applying the correction model to thephotolithography tool to adjust for the topography or other uniquephysical characteristics in the pattern area of the reticle.

Yet another method of implementing a reticle in a photolithography toolin accordance with the invention comprises obtaining qualitative datafrom the reticle at a location remote from the photolithography tool,and determining a correction model to apply to the photolithography toolfrom the qualitative data. The correction model may be calculated usinga computer located either (a) remotely from the lithography tool or (b)with the lithography tool. This method continues by applying thecorrection model to the photolithography tool to adjust for topographyor other unique physical characteristics in the pattern area of thereticle.

Additional embodiments of the invention are directed to methods forprocessing micro-device wafers. One embodiment of such a methodcomprises obtaining qualitative data from within a pattern area of areticle. This method continues by determining a correction model toapply to the photolithography tool from the qualitative data, andadjusting the photolithography tool to compensate for features of thereticle based on the correction model. This method further continues byexposing the wafer to an exposure radiation to transfer a pattern in thepattern area of the reticle to a wafer in the photolithography tool.

Additional embodiments of the invention are directed toward a system forimplementing a reticle in a photolithography tool. One embodiment ofsuch a system comprises a measuring station located remotely from thephotolithography tool and a correction module. The measuring station isconfigured to obtain qualitative data from within a pattern area of areticle. The correction module includes a computer operable mediumcontaining instructions that use the qualitative data to determine acorrection model for adjusting the photolithography tool to compensatefor features of the reticle in the pattern area.

Various embodiments of the invention are described in this section toprovide specific details for a thorough understanding and enablingdescription of these embodiments. A person skilled in the art, however,will understand that the invention may be practiced without several ofthese details, or that additional details can be added to the invention.Well-known structures and functions have not been shown or described indetail to avoid unnecessarily obscuring the description of theembodiments of the invention. Where the context permits, singular orplural terms may also include the plural or singular term, respectively.Moreover, unless the word “or” is expressly limited to mean only asingle item exclusive from the other items in reference to a list of twoor more items, then the use of “or” in such a list is to be interpretedas including (a) any single item in the list, (b) all of the items inthe list, or (c) any combination of the items in the list. Additionally,the term “comprising” is used throughout to mean including at least therecited feature(s) such that any greater number of the same featureand/or types of other features or other components are not precluded.

B. Embodiments of Methods for Manufacturing Reticles for Use inPhotolithography Tools

FIG. 1 is a flow chart illustrating a method 100 for manufacturing areticle for use in a photolithography tool in accordance with anembodiment of the invention. The illustrated embodiment of the method100 includes a first stage 110 comprising providing a substrate having apattern area and a perimeter region outside of the pattern area. Thesubstrate is typically a piece of glass or other article having thedesired optical properties for transmitting the imaging radiation usedin the photolithography tool. At this stage of the method, the substratecan have a pattern already formed in the pattern area, or the substratecan be provided without having a pattern formed in the pattern area. Ingeneral, the pattern area is the region of the substrate wherein apattern is or will be formed. The pattern area is accordingly located sothat an exposure can transfer a pattern formed in the pattern area to awafer when the reticle is used in a photolithography tool.

The method 100 continues with a second stage 120 comprising obtainingqualitative data indicative of at least one physical characteristic ofthe substrate from points or areas within the pattern area and/or theperimeter region. In the illustrated embodiment of the method 100, thequalitative data is obtained remotely from the photolithography tool.For example, a metrology tool or other type of measuring tool can belocated at a measuring station separate from the photolithography tool.Suitable remote locations for obtaining the qualitative data includemask vendors or mask shops where the substrate is qualified beforeforming a pattern and/or where a pattern is formed in the pattern area.The remote locations for obtaining the qualitative data, however, caninclude any other location where the particular physical characteristicof the substrate can be measured without interrupting the processing ofwafers in the photolithography tool.

FIG. 2A is a schematic view of the second stage 120 of the method 100,and

FIG. 2B is a schematic top plan view of a reticle 220 being processed inthe second stage 120. Referring to FIG. 2A, the second stage 120 canoccur at a measuring tool 200 having a non-contact measuring unit 210including an illumination source 212 and a detector 214. The measuringunit 210 can be an interferometer, scatterometer, ultrasonic probe,topology tool, or any other type of device that can determine a physicalcharacteristic indicative of the contour, curvature, or other feature ofthe reticle 220. Referring to FIGS. 2A and 2B together, the second stage120 includes placing the reticle 220 in the measuring tool 200. Thereticle 220 can have a substrate 221 including a pattern area 222 and aperimeter region 224. The illumination source 212 generates anon-contact measuring energy 211 (e.g., a laser beam), and the detector214 detects a return signal of the non-contact energy 211. The tool 200operates the measuring unit 210 and/or moves the reticle 220 such thatthe beam 211 measures a physical characteristic at a plurality of pointsin the pattern area 222 of the reticle 220 and/or the perimeter region224.

Referring to FIG. 2B, for example, the second stage 120 can includemeasuring the elevation of the surface or other aspects of the surfacetopology of the substrate 221 at points P(x₁, y₁) through P(x_(n),y_(n)) throughout a large number of points in the pattern area 222. Eachmeasurement point P is actually a spot having a small area. The secondstage 120 can further include measuring the surface elevation ortopology at alignment marks 226, other types of fiducials, or theperimeter region 224. The number of measurement points P in the patternarea 222 and/or the perimeter region 224 can be as low as a few pointsto as high as several thousand points. In several applications, thenumber of measurement points P in the pattern area 222 can be fromapproximately 10 to approximately 5,000, and more preferably fromapproximately 50 to approximately 5,000, and still more preferably fromapproximately 250 to about 2,500. The number of measurement points P istypically a function of the desired resolution and the time availablefor obtaining the qualitative data. A large number of measurement pointsP will result in a more accurate assessment of the contour and shape ofthe reticle 220 within the pattern area 222, but a lower number ofmeasurement points P reduces the measurement time and data processingtime. In practical applications, a large number of measurement points Pmay be used because the qualitative data is obtained remotely from thephotolithography tool such that the measurement time is not an issue instage 120 as it is when the photolithography tool is used to measure thereticles in conventional processes.

Referring again to FIG. 1, the method 100 further includes a third stage130 comprising determining a correction model based at least in part onthe qualitative data. The correction model can be calculated orotherwise ascertained remotely from the photolithography tool, or thecorrection model can be ascertained in a module or other component ofthe photolithography tool. The correction model determined in the thirdstage 130 preferably sets forth the adjustments for the imaging opticsand/or the wafer stage of the photolithography tool to compensate forthe curvature or other features in the pattern area 222 of the reticle220.

One aspect of the method 100 is that the inventors have discovered thatthe curvature and other selected features of a reticle substratetypically do not change throughout the process of manufacturing thereticle. As a result, the flatness or other physical characteristics ofthe reticle substrate can be measured remotely from the fabrication linebefore or after a pattern is formed on the reticle, and before loadingthe reticle into a particular photolithography tool. The particularphotolithography tool, therefore, does not need to be taken off-line tomeasure the contour of the reticle in the perimeter region. The method100 is accordingly expected to enhance the efficiency of manufacturingsemiconductor devices and other types of micro-devices.

Another aspect of several embodiments of the method 100 is that thecorrection model determined in the third stage 130 is expected toprovide better data to compensate for the unique features of aparticular reticle. Unlike the conventional processes that measurepoints only in the perimeter region of a reticle, several embodiments ofthe method 100 obtain the qualitative data from within the pattern area222 of the reticle 220. As a result, the qualitative data used todetermine the correction model in the third stage 130 includes actualmeasurements of the pattern area 222 instead of an estimated contour ofthe pattern area based on measurements taken in the peripheral area.Several embodiments of the method 100 can further enhance the accuracyof the qualitative data by obtaining a large number of measurementpoints in the pattern area. Therefore, the method 100 is expected toresult in a highly accurate assessment of the physical characteristicsof the pattern area 222 for calculating a highly accurate correctionmodel.

C. Methods and Systems for Implementing a Reticle in a PhotolithographyTool

FIG. 3 is a flow chart illustrating a method 300 in accordance with anembodiment for implementing a reticle in a photolithography tool inaccordance with the invention. The method 300 includes a first stage 310comprising obtaining qualitative data from within a pattern arearemotely from the photolithography tool, and a second stage 320comprising determining a correction model for the photolithography toolbased on the qualitative data obtained in the first stage 310. The firstand second stages 310 and 320 shown in FIG. 3 can be similar to thesecond and third stages 120 and 130, respectively, shown in FIG. 1. Themethod 300 further includes a third stage 330 comprising applying thecorrection model to the photolithography tool. Several aspects ofapplying the correction model to the photolithography tool are best setforth with reference to the environments in which a reticle is measuredand implemented.

FIG. 4 is a schematic illustration of one embodiment of a system 400 forimplementing a reticle in a photolithography tool 402. The system 400can include a measuring station 410 located remotely from thephotolithography tool 402. As described above, the measuring stationobtains the qualitative data from within a pattern area and/or aperimeter region of a reticle to ascertain a physical characteristic ofthe pattern area. The system 400 further includes a correction module420 having a computer operable medium that contains instructions whichuse the qualitative data to determine a correction model for adjustingthe photolithography tool to compensate for the measured physicalcharacteristic of the reticle. The correction module 420 can be hardwareand/or software that is located with the measuring station 410 as shownin solid lines in FIG. 4. In an alternative embodiment, the correctionmodule 420 is optionally separate from both the measuring station 410and the photolithography tool 402 (as shown in dotted lines), or thecorrection module 420 is optionally a component associated with thephotolithography tool 402 (shown in dashed lines).

In operation, the correction module 420 determines a correction modelthat is transmitted to the photolithography tool 402 by a communicationlink 422 (e.g., a wired or wireless link). The photolithography tool 402uses the correction model to adjust components of the photolithographytool 402 to compensate for the unique features of the pattern area ofthe reticle. For example, the photolithography tool 402 can include acontroller 430 having a processor 432 that incorporates the correctionmodel from the correction module 420 into the operation of thephotolithography tool 402. The controller 432, for example, can adjustany one of the following items either individually or in variouscombinations with each other to compensate for the measured features ofthe reticle 220: an illumination source 440; illumination optics 450;imaging optics 460; and/or a wafer stage 470 upon which a wafer W ispositioned.

Several embodiments of the third stage 330 of the method 300 illustratedin FIG. 3 apply the correction model to the photolithography tool byregistering or otherwise associating the measurement points P (FIG. 2B)on the reticle 220 with the reference system of the photolithographytool 402 (FIG. 4). For example, one embodiment of the third stagefurther comprises registering a measurement reference frame in which thequalitative data was obtained in the measurement station 410 with aprocess reference frame of the photolithography tool 402 in which apattern is transferred to the wafer W. The measurement reference framecan be registered with the process reference frame by registeringfiducial marks on the reticle 220 in both the measurement and processreference frames, and then determining an offset to apply to themeasurement points P for calculating the coordinates of the measurementpoints P in the process reference frame. Based on the registeredcoordinates of the measurement points P in the process reference frameof the photolithography tool 402, the controller 430 can operate thedevice to adjust the optics and/or the wafer stage 470 according to thecorrection model determined in the correction module 420.

FIG. 5 is a flow chart illustrating a method 500 for implementing areticle in a photolithography tool in accordance with another embodimentof the invention. The method 500 includes a first stage 510 comprisingobtaining qualitative data from within a pattern area of the reticlethrough which an exposure radiation is to be directed for transferring apattern from the reticle to a wafer. The method 500 further includes asecond stage 520 comprising determining a correction model to apply tothe photolithography tool based on the qualitative data, and a thirdstage 530 comprising applying the correction model to thephotolithography tool to adjust for unique physical characteristics inthe pattern area of a reticle. The method 500 shown in FIG. 5 can besimilar to the method 300 illustrated in FIG. 3, but the qualitativedata is not necessarily obtained remotely from the photolithographytool. Otherwise, the second stage 520 and the third stage 530 can besimilar to the second and third stages 320 and 330, respectively,discussed above with reference to FIGS. 3 and 4.

FIG. 6 is a flow chart of a method 600 for implementing a reticle in aphotolithography tool in accordance with still another embodiment of theinvention. The method 600 illustrated in FIG. 6 includes a first stage610 comprising obtaining qualitative data from the reticle at a locationremote from the photolithography tool. The qualitative data obtained inthe first stage 610 is not necessarily limited to data from within thepattern area of a reticle, but can include (a) data from only aperimeter region of the reticle, (b) data from within only a patternarea of a reticle, or (c) data from within both a perimeter region andthe pattern area of a reticle. The method 600 further includes a secondstage comprising determining a correction model to apply to thephotolithography tool, and a third stage 630 comprising applying thecorrection model to the photolithography tool.

FIG. 7 is a flow chart illustrating a method 700 for processing amicro-device wafer in accordance with an embodiment of the invention.The method 700 includes a first stage 710 comprising obtainingqualitative data from within a pattern area of a reticle. In general,the first stage 710 includes obtaining data regarding the contour orother physical characteristics of the pattern area where an exposureradiation from the photolithography tool passes toward the workpiece.The method 700 further includes a second stage 720 comprisingdetermining a correction model based on the qualitative data to apply tothe photolithography tool, and a third stage 730 comprising adjustingthe photolithography tool to compensate for features of the reticle. Thethird stage 730 adjusts the photolithography tool based on thecorrection model determined in the second stage 720. The method 700further includes a fourth stage 740 comprising exposing the wafer to anexposure radiation to transfer a pattern in the pattern area of areticle to a wafer in the photolithography tool. The fourth stage 740can include stepping and/or scanning the pattern across the wafer bymoving the wafer stage and adjusting the optics according to processesknown in the semiconductor fabrication industry.

From the foregoing, it will be appreciated that specific embodiments ofthe invention have been described herein for purposes of illustration,but that various modifications may be made without deviating from thespirit and scope of the invention. For example, various aspects of eachof the foregoing embodiments described above can be combined with eachother in additional embodiments of the invention. Accordingly, theinvention is not limited except as by the appended claims.

1. A system for implementing a reticle in a photolithography tool, comprising: a measuring station located remote from the photolithography tool, wherein the measuring station is configured to obtain qualitative data from within a pattern area of a reticle that is to be used in the photolithography tool; and a correction module including a computer operable medium containing instructions that uses the qualitative data to determine a correction model for adjusting the photolithography tool to compensate for features of the reticle in the pattern area and provides the correction model to the photolithography tool.
 2. The system of claim 1 wherein the measuring station comprises an interferometer.
 3. The system of claim 1 wherein the measuring station comprises a photoluminescent measuring tool.
 4. The system of claim 1 wherein the measuring tool comprises a laser and a detector configured to measure a parameter related to surface non-uniformities of the substrate at a plurality of locations in the pattern area.
 5. The system of claim 4 wherein the parameter comprises a variance from a reference plane.
 6. The method of claim 1 wherein the computer-operable medium contains instructions that cause the photolithography tool to adjust at least one of an image optic of the photolithography tool and the wafer stage of the photolithography tool to compensate for non-uniformities in the pattern area. 